Since the release of jQuery 2.0 we have been two varieties of jQuery which include the 2.x branch are smaller and faster but don’t support older browsers – specifically they don’t support Internet Explorer before IE9 while the 1.x.x branch is continuing to accommodate IE6, 7, and 8. 2.1.0, the 2.x now include support for the non-traditional web environments such as node.js and browser plugins for Chrome and Firefox. And while both updates bring a host of bug fixes and support for more web environments, developer will see no changes to the APIs. Check out the full details here on the jQuery blog.